Apparatus and method for producing collagen tubing by continuous extrusion



March 3, 1964 E. R. LIEBERMAN 3,122,788

APPARATUS AND METHOD FOR PROOUOTNG OOLLAOEN .TUBING BY CONTINUOUS EXTRUSTON Filed Jan. 16, 1961 5 Sheets-Sheet 1 TT- c f March 3, 1964 E R. LIEBERMAN 3,122,788

APPARATUS AND METHOD FOR PRODUCING COLLAGEN TUBING BY CONTINUOUS EXTRUSION Filed Jan. 16, 1961 5 Sheets-Sheet 2 TlEL.

50 Z/5 236 295 252 ZZZ 236 ATTORNEYS.

March 3, 1964 E. R. I IEBERMAN 3,122,788

APPARATUS AND METHOD FOR PRoDucING coLLAGEN TUBING BY CONTINUOUS EXTRUSION l Filed Jan. 16, 1961 5 Sheets-Sheet 5 1 .3. T :i f/

INVENTO WHA/f4 /P. fing/ww March 3, 1964 E, R, LIEBERMAN 3,122,788

APPARATUS AND METHOD FOR PRODUCING COLLAGEN TUBING BY CONTINUOUS EXTRUSION Filed Jan. 16, 1961 5 Sheets-Sheet 5 INVENTOR {MAA/afl /F M35i/VAN ATTO R N EYS United States Patent() APPARATUS AND METHOD FUR PRGDUC- ING CGLLAGEN TUBlNG BY CONTlNUQUS EXTRUSIN Emanuel Roy Lieberman, Somerville, NJ., assignmto .lolirison 8: Johnson, a corporation of New Jersey Filed Jan. 16, 1961, Ser. No. 82,933 12 Claims. (Cl. lll-12) The present invention relates to the manufacture of tubular collagen products such as synthetic sausage casings and, more particularly, to an improved apparatus and method for producing collagen tubing by continuous extrusion.

The product of the invention, after suitable finishing treatments, is particularly adapted to be utilized as an edible casino for fresh pork sausages which must be cooked by the consumer, as well as sausages of the wiener or frankfurter type. T he latter sausages are processed by being smoked and cooked by the packer and are generally reheated before they are consumed. When such sausages are provided with edible casings, it is unnecessary to remove the casing before the sausage is eaten.

Natural casirigs produced from the intestines of sheep, hogs and cattle have certain inherent shortcomings including non-uniformity and porosity of casing wall, variations in casing size and edibility, and wide iluctuations in market price and availability. Except for some made from sheep intestines, they are tough and hard to masticate. lso, natural casings are difficult to clean and prepare for human consumption. In addition, the thickness of the wall and diameter of natural casings will vary, causing diiculty during modern high speed stuffing. In view of these deficiencies, many attempts have been made to produce better edible synthetic casings from protein sources such as collagen.

The present invention provides a new and useful extruder and a method of extrusion by which tubing is produced from animal collagen in a form from which synthetic casings of adequate strength can be produced but which possess unusual tenderness in eating as well as the ability to resist melting and shrinking or bursting during cooking.

Definitions For the sake of clarity and brevity, certain terms hereinafter used in the specification and claims, which will be useful in understanding the invention, are defined as follows:

By term collagen fibril is meant the structural unit of coilagenous tissues made up of many thousands or even millions of tropocollagen units. The collagen fibril, as it is found in cownide, measures in the completely dehydrated state about 50 to 1,000 Angstroms in diameter and is of indenite length. Cowhide collagen fibrils measuring 20,000,000 Angstroms (two millimeters) in length have been observed. The collagen iibrils in bovine hide are arranged in bundles to form collagen bers measuring thousands of Angstroms in diameter and of indeiinite ength.

Cowhide collagen fibers (as distinguished from fibrils) have been observed which measure about 10,000 to 20,000 Angstroms in the dehydrated state, and larger collagen iibers measuring as much as one millimeter (10,000,000 Angstroms) in diameter in their dehydrated state are believed to exist. Each collagen fiber contains hundreds or even thousands of brils, all bound together by a sheath. rl`lie collagen bers, in turn, are organized into bundles of collagen tibers that are large enough to be seen by the naked eye and form the familiar fibrous network visible in hides of all sorts.

'ice

The term swollen collagen fibril in the context of this application is the state assumed by collagen librils after fragments of cowhide or the like have been progressively reduced in size and the librils therein are swollen to more than times their original volume in a suicient quantity of a weak acid solution. The pressure of the swelling of the constituent fibrils will rupture the relatively inelastic ber sheath that surrounds the brils, thus destroying the identity of the ber. The swollen collagen fibrils may then be separated from remnants of the fiber sheath by ltration. It must be emphasized, however, that to achieve disruption of the liber structure by swelling, the ratio of swelling lluid to collagen must be high.

The term uid mass of swollen collagen tibrils is herein applied to Vsuch a mass after tfiltration and when ready for extrusion. In that state, the separated liber sheaths have been removed. lu accordance with the present invention, such a fluid mass of swollen collagen fibrils should contain from about 2.5% to about 6% of collagenous tissue on a dry-weight basis.

ri`ypical casings produced from tubing extruded in accordance with the present invention have the following illustrative properties when tested on an Instron tensile tester b'y the method described in copending application Serial No. 82,935, liled as of even date herewith. Each casing sample is heated to 99 C. with live steam prior to testing.

The change of length due to shrinkage of a three-inch sample of the casing heated to 99 C., with live steam amounts to from about 1.0 inch to about 2.0 inches.

The strain in inches per pound of stress is from about 2.0 to about 20.0 inch pounds.

The hot tensile strength is from about 0.10 pound to about 1.00 pound.

The shrink tension is from about 0.08 pound to about 0.50 pound.

The percentage recovery (length of the casing at the break point) divided by original length of sample being tested times 100, amounts to from about 81 to about 150.

The burst strength is at least about l0 to 28 pounds per square inch. Burst strength is the air pressure in pounds per square inch required to burst dry extruded collagen casing having a wall thickness of one mil. T he values of burst strength expressed in this specification were determined on a Perkins Mullen Tester (Model C). Fluid under uniformly increasing pressures expands against a distensible rubber diaphragm and, simultaneously, into a Bourdon pressure gauge. The material to be tested is clamped securely to a metal plate through which the diaphragm is free to expand through a circular opening against one square inch of its surface. As the sample distorts under pressure, the diaphragm assumes the exact contour of the material.

General Description Natural casings are formed of a network of generally evenly distributed interlaced collagen libers and r'iber bundles and thus inherently possess the necessary strength characteristics, while those from the optimum sheep gut product Vare Valso edible when cooked. However, synthetic collagen casings heretofore available have not been able to satisfactorily duplicate the natural product, particularly as to tenderness and cooking responses. t has heretofore been proposed to produce an articial collagen casing from fibrous animal material such as, for example, dehaired hide which has been subjected to conventional liming treatments. Collagen in such limed iibrous material is converted by mechanical disintegration and the swelling action of acids into a paste of fiber bundles and fibers which is then extruded to form a tube. Such paste or pasty masses commonly have a solids content of the order of to 25%, although in some cases the solids have been as low as about 8%. These pastes are extruded under relatively great pressures of the order of hundreds of atmospheres, required because of the highly viscous nature of the relatively dry pasty masses. The tubes so produced are relatively thick, tough and difficult to masticate after cooking.

These undesirable properties of prior artificial collagen casings are further increased and complicated by the types of treatments to which the tubes are commonly subjected after extrusion. Such casings, when stuffed with edible meat, will not survive in the frying pan because cooking temperatures cause the collagen casing to shrink, extruding the meat product.

In accordance with the present invention, it has been discovered that an exceedingly thin-walled tube of collagen casing material may be produced from a uid mass of swollen collagen fibrils having a solids content much lower than heretofore used, i.e., on the order of at least 2.5% and less than 6%, preferably about 3.5% to 5%. It has been observed that collagen iibrils in unlimed cowhide will Yswell to more than 100 times their original volume if comminuted cowhide, progressively reduced in particle size to very small dimensions, is placed in a suflicient quantity of a weak acid solution, such as 1.2% of lactic acid in water. The pressure of the swelling of the constituent fibrils will rupture the relatively inelastic iber sheath that surorunds the fiber containing the fibrils,

. thus destroying the identity ofthe ber. The swollen collagen fibrils may then be separated from remnants of the fiber sheath by filtration. Thin-walled tubular casing material formed by extrusion in accordance with the present invention from such a relatively watery mass of exceedingly fine swollen fibrils, when subjected to suitable post-extrusion treatments, will produce sausage casings which are very tender and so easy to masticate that in eating, they can scarcely be distinguished from the sausage meat itself. Nevertheless, sausage casings prepared in accordance with the present invention possess sufiicient tensile strength and burst strength that they may be shirred, stuffed and linked in commercial practice without rupture or Vundue stretching. Moreover, such casings have been found to survive the stresses and temperatures involved in cooking in the frying pan so that there is substantially no shrinkage, rupturing or melting of the casing or extrusion of thermeat product therefrom during the cooking process.

However, the utilization of fluid masses of swollen collagen fibrils (i.e., those inV which the collagen material hasvbeen reduced to particles of fibrillar size and in which the proportion of collagen solids in the swollen fibrillar mass is of the low order above-described) introduces problems in extruding and in handling the extruded tubular body from the moment it leaves the orifice of the extruder until it has been dried and reduced to the ultimate size in which it is to be shirred and later used. The delicate nature of the swollen collagen fibrils is such that the iiuid mass thereof must be handled carefully during the extrusion process itself to avoid degradation of the material as well as undesirable layering and the formation of weak spots in the final product.

While the preferred percentages of collagen solids heretofore givenfor practice of the invention are not highly critical to the first decimal point, the extrusion and post-extrusion handling of fluid masses of swollen collagen fibrils below about-2.5% of collagen solids is impractical. Although extrusion of such a mass having a solids coutent of between 2% and 2.5% is theoretically possible, the watery nature thereof'reduces the Visco-elastic properties of the mass and introduces post-extrusion problems of handling and so increases the time required for coagula- Y tion that its use is quite impracticable.

On the other hand, a iiuid mass of swollen collagen fibrils having a collagen solids content of about 4% is 75 within the above-described preferred and practicableY ranges of collagen solids, the extrusion of such a watery or low-solids material produces an exceedingly fragile tubular body which must be handled with the greatest delicacy and care during the subsequent treatments in which it is coagulated, hardened, plasticized and dried.

In the practice of the invention, when the mass of swollen collagen solids leaves the extruder orifice, it is essentially a liquid which must be immediately given a coagulating treatment in order to preserve the shape imparted to the liquid as it leaves the mouth of the extruder and is still travelling under the kinetic energy imparted by the extrusion force. Once this initial coagulation takes place, the extruded tubular body possesses tangible form `and integrity of its own but nevertheless remains weak,

fragile and subject to rupture as it passes in the wet state through subsequent conditioning treatments. In spite of its fragile nature, the exacting requirements of continuous production are such that this initially watery tubular body must be reduced from an initial wall thickness at the extruder orifice or, eg., about 14 mils to an ultimate Ywall thickness of about one mil while preserving the invfiow when they encounter an obstacle in their path of ltravel during extrusion. These obstacles usually include a collagen agglomerate in the plastic mass which is retained or caught in the narrow opening of the extrusion chamber. Heretofore, because the basic collagen structure, composed of fibers and fiber bundles, was of a much larger size order than swollen fibrils, and because there was no appreciable homogenization during extrusion, cas- Vings often were produced with a generally longitudinal seam or fauit in the casing wall formed by collagen fibers matted or gathered by a blocked extruder. This fault or seam materially reduced the strength of such casing.

Further, swollen collagen fibers and ber bundles readily tend to become oriented in the general direction of extrusion or in other directions as determined bythe extruder construction. Orientation in a particular direction throughout a substantial part of the thickness of a casing makes the casing readily susceptible to splits or tearingin the direction of orientation, the tear line occurring generally in the area between the oriented collagen bers. Attempts have been made to improve the tear strength by randomly orienting'th'e ibers by a tan- Vgling, matting or felting action, but such haphazard a1'- rangements of fibers so produced have not resulted in a satisfactory product.

A phenomenon inherent in fiuid masses of swollen collagen material, either fibrous or nbrillar, creates an irnportant and ditdcultproblem in the formation of articles produced by extrusion thereof. When such a fluid collagen mass undergoes conditions of fow, it is affected in such a manner that it remembers the boundary conditions under Vwhich it has been fiowed. W'hen two such fiuid masses, so preconditioned, are brought into contact with each other, the boundary area defined by their contasting surfaces persists in VVthe uid mass and persists even in forms into which such mass is subsequently extruded or othe wise shaped. The formation and persistence of such boundary areas in articles extruded from collagen masses in which they exist, creates areas of weakness which permanently wealzen the product so formed.

Thus if a Fluid mass of swollen collagen Librils is caused to ow into an annular cavity from a peripheral inlet, the flowing mass is divided and then the divided streams ilow together somewhere in their annular paths. The area where the divided streams meet and merge remains in the memory of the material as a persistent boundary area and becomes, in use, an area of weakness. This Weak boundary area will persist in the subsequent handling of the material unless and until the iluid mass is so thoroughly blended at the boundary area that such area is obliterated.

The present invention overcomes or avoids this boundary area problem by applying continuous and intensive rotary shearing forces to the mass of material to be eX- truded throughout its passage through the extruder. By this means the prior memory of the boundary area is obliterated and no boundary eifect is permitted to occur during the extrusion process. The iluid material is never divided into streams or separate flows having boundaries which meet each other in the extrusion process, but always travels in complete circular paths both radially outwardly and inwardly during its movement through the extruder.

In practice, sausage casings are subjected to tension or pull in a direction parallel to the longitudinal axis of the casing tube during the manufacturing steps of drying, shirring and linking. 1n addition, upon stuffing and cool;- ing of the meat emulsion therein, the casing is subjected to internal bursting pressures. A satisfactory casing should possess suciently high and uniform strength characteristics to resist these forces, while not being tough, thick or otherwise ditlicult to chew.

The strength of a casing made from swollen collagen fibrils apparently is derived from the collagen fibrils constituting such casing. The weakest section of any such collagen casing generally is believed to be the area between the individual collagen iibrils after they have been swollen and dried in situ. Thus an important factor affecting the strength of a casing is the collagen fibril distribution therethrough. Uniform or homogeneous distribution of the collagen fibrils, particularly in random orientation throughout tie casing Wall, eliminates the development of weak spots in the casing wall due to the absence of suthcient fibrils at the weakened location. The appearance and internal microscopic structure of casing material having these properties are more fully disclosed and claimed in application Serial No. 82,935, filed as of even date herewith.

Objects lt is therefore an object of this invention to provide a novel extruder mechanism which produces a collagen casing tubing formed of swollen tlbrils having improved strength characteristics.

it is a further object of this invention to provide a novel entraider appmatus for continuously eXtrud-ing from a iluid lmass of `swollen collagen iibn'ls, tubing for collage oasihgs having a generally uniform collagen bril distribution therethrough.

Another object of the invention is to provide a new and useful exhudelr method and means for avoiding the occurrence of boundary areas, such as referred to above, in the fluid mass of swollen collagen fibrils and to obliterate any such boundary areas which may have been formed in said mass prior fto its having been passed into and through the extruder.

Another obj ct o-f the invention is to provide extruder mechanism for continuously extruding a collagen tubing from a iluid mass of swollen collagen ybrils wherein the extruder elements impart a transverse rotary shearing action rto the fluid mass during the extrusion process to eliminate any boundary cifect in :the collagen mass.

lt is also an object of the invention to provide a novel method of extruding a continuous tube of collagen from a fluid mass of swollen collagen fibrils Iby subjecting the -luid rnass to transverse rotary shearing actions to eliminate boundary effects in the collagen mass and flowing the fluid mass in continuous circular paths during the extrusion process.

The foregoing and other objects may be attained in `accordance with -t-he present invention which, in its various aspects, includes a novel apparatus for the manufacture of a synthetic collagen casing and novel steps in the man1 facture of such product.

Referring now in detail to present preferred practices by `which the fluid :mass of `swollen collagen fibrils is prepared for extrusion in yaccordance ywith the invention, said preferred method utilizes as the iraw material fresh (frozen or sted) dehaired hides, preferably bovine, which have not been treated with lime or other alkaline agents or with enzymes. Representative examples illustrating the preparation of such preferred mass of swollen collagen fibrils ere disclosed in copending `application Serial No. 64,664, tiled October 24, 1960. That application also generally discloses, primarily in a chemical sense, the other treatment steps to which the extruded tubular body of swollen collagen fibrils is subjected in carrying out the method steps lerrrbody-ing the present invention. Parts taken from Example l of that `application are set forth below `for the purpose of illustrating and explaining the various method .and physical treatment steps employed in lthe present invention, but the invention is not limited to such example, as will be clear to those skilled in the ll'vll.

ln said example, fresh steer hides are Washed lwith cold water at 13 C. or less in a rotating `drum for 10 to 24 hours. After wash-ing, the lhides are defleshed with a scnaping machine and the hair and epidermis me cut oil" with a horizontal band knife. This preliminary cleaning is accomplished with standard t-annery equipment.

rl`he remaining hair and poorly cleaned sect-ions are cut olf by hand land composites are prepared from live hides. The hide composites are then `cuit into one-half to four square inch sections and reduced to pulp lby three passes ythrough a meat grinder, each pass being a liner grind. rhe first and second passes are through 18 and 8 millimeter holes, respectively. The nal grind is through holes 1.5 millimeters in diameter. lt is important during the ygrinding process to keep the pulp .be-low 20 C. This may be done by adding crushed ice to the hide sections as they are fed to the grinder.

The ground pulp is nent diluted with tap water at 16 C. :to give a smooth slurry con-taining 7.4% dry solids. This slurry parts) lis then treated with 125 parts of a 2.4% lactic `acid water solution using `an inline mixer such as that manufactured by Cherry Burell (Model 24) 'to form a homogeneous tmass of swollen collagen fibrils. it is important during this acid swelling step also that the temperature be maintained below about 25 C. The mixture so obtained contains 3.7% hide solids and 1.2% lactic acid. After the pump `is blended Iwith acid, the mass of swollen collagen fibrils is further dispersed in a suitable homogenizer `such as 1a Manton-Gamin homogenizer (Model 125-i l-5BS), fitted with `a two-stage valve and operated with a 1,50() psi. drop per stage. In the ultimate l mass of swollen collagen fibrils soprepared, the inilu dividual fibrils are freed from the ber bundles and bers released yfrom the ber sheaths. They take up all liquid tand swell from an original diameter of the orde-r of 300 A. to 1,980 A. to a freshly swollen (one day old) maximum diameter of the order o-f 15,000 A.

The fluid mass of swollen collagen fibrils obtained by `the foregoing method (which is given Aby way of illustraltion and without specific limitation) is then filtered through a seven-mil tfilter screen to remove unswollen coll-agen 7 and non-collagenous materials, after which it is ready for extrusion.

In accordance with the invention, the desired distribution of the collagen fibrils in the casing wall is eected by the use of improved extruder mechanism which utilizes passageways between planar elements which are relatively rotatable about a central axis extending in the general direction of extrusion, preferably vertically. The inner planar element is preferably disc-lilf.e, of a diameter substantially greater than its axial depth and having a planar upper surface generally perpendicular to the direction of extrusion. The upper surface of the inner element or disc is in adjacent spaced relationship with a cooperating planar face of the outer element, forming an upper flat, thin extrusion passageway therebetween communicating with an annular discharge chamber at the center of the disc which extends parallel to the general direction of extrusion.

A uid mass of swollen collagen fibrils is pressure-fed in the general direction of extrusion and directed against the underface of the inner extruder element or disc into the space between the inner and outer elements. The feed pressure directs the iluid mass radially outwardly through the relatively deep lower passageway toward the peripheryk of the disc where it passes around the circumferential edge of the disc into the upper planar extrusion passage, which is preferably shallower than the rst or lower passage.

In said upper extrusion passage, the continued rotational movement of the extruder member or members creates a circular tension in the lluid mass of swollen collagen bn'ls which exhibits visco-elastic properties. A viscoelastic material is one having both elastic and viscous properties; that is to say, although the material be viscous, it possesses a certain elasticity of shape. By subjecting a Visco-elastic material to rotational forces, a circular tension is created therein which contracts the material radially toward the center of rotation, rainer than outwardly as is normally the case with other kinds of uids, eg., Water. This phenomenon is called the Weissenberg eect. The circular tension thus created in the Visco-elastic mass of swollen collagen fibrils urges the collagen mass radially inwardly from the periphery of the disc along the upper extrusion passage toward the central annular discharge chamber whence it is extruded in the form of a tube into a dehydrating or coagulating bath.

Thus the novel extruder apparatus of the present invention utilizes the Visco-elastic property of the swollen librillar fluid mass to substantially reduce extrusion pressures. Further, by subjecting the collagen mass to smooth shearing action by the extruder elements in a direction transverse to the general direction of extrusion, any matted or gathered collagen agglomerates are dispersed, effecting an even distribution of individual collagen fibrils in the uid librillar mass entering the discharge chamber.

The desired distribution of the swollen collagen iibrils is attained by subjecting substantially all of said brils in the narrow extrusion passages to transverse, smoothlyapplied, rotational forces acting in spaced planes parallel to the radial extrusion forces. By subjecting the fibrils toparallel planar forces, it is believed that a parallel planar distribution of iibrils is produced while the rotational shearing forces effect a random orientation of the ibrils within such parallel planes, although applicant does not intend to be limited to this theory of operation as expressed here or elsewhere in` his application. Concornitantly, the iiuid iibrillar mass is protected from disruption by grinding, turbulence and disruptive contacts as it passes through the smooth planar extruder. Y

Byrthe process of the present invention, a collagen tube is extruded by iiowing a huid, Visco-elastic mass of swollen collagen librils upwardly under pressure through a passages in the '8 `smooth inner annular Zone concentric about Va longitudinal axis extending in the general direction of extrusion, directing the ilow of swollen fibrils during a portion of its travel through the annular zone smoothly radially outwardly from and then smoothly radially inwardly (under the circular tension forces of the Neissenberg etlect) into the annular exit zone. This is done through interconnected, spaced planar zones extending laterally of the general direction of extrusion, and subjecting the swollen collagen ibrils in the planar zones to shearing forces transverse to the Vgeneral direction of extrusion to uniformly distribute the collagen librils in the mass reentering the annular Zone.

it is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory but are not restrictive of the invention.

For a more complete understanding of the invention, reference should be had to the accompanying drawings, wherein:

FIG. l is a vertical sectional View of one embodiment of the present invention;

FIG. 2 is a vertical sectional view, similar to FIG. l, of a second embodiment of the present invention;

FIG. 3 is a vertical sectional View, similar to FIG. 1, of a third embodiment of the invention;

FIG. 4 is a vertical sectional View, similar to FIG. 1, of a fourth embodiment ot the present invention;

FIG. 5 is a greatly enlarged diagrammatic plan View of the wall of an extruded tubular body illustrating the random distribution of the collagen iibrils believed to occur; and

FIG. 6 is a cross-sectional View of the wall shown in FG. 5, taken along line 6-6 of FIG. 5;

Referring now in detail to the preferred embodiments of the invention shown by way of example in the accompanying drawings, FIG. 4 shows in somewhat diagrammatic form a structure capable of carrying out the underlying principles of the invention in a relatively simple manner. In this form, the homogenization and distribution of the collagen brils are accomplished 'oy means of a single rotating disc element.

As shown, the extruder of FIG. 4 comprises tube or conduit lill? through which the fluid mass of swollen collagen fibrils is introduced under suitable hydraulic pressure into the interior of the extruder. The extruder construction comprises a cylindrical housing 102 which is centrally apertured to provide a cylindrical vertical passageway tlS therethrough.

Axially disposed in housing lll?. is a hollow mandrel M8. The lower end of the mandrel passes through a base 169 and is secured to a bracket itil carried Vby suitable framework (not shown) which supports the extruder in vertical position.

Housing 192, is covered by a flat cylindrical cap 3164 which is fixed to the upper flat face 1&3 of housing 02 by means of countersunk bolts lltl. Cap 16d is also centrally apertured at lilo to provide the mouth or central opening for the extruder from which the extruded tubular body C is fragnentarily shown, rising vertically from the extruder orifice.

The annular extruder orice 11i) is formed between the aperture 1&6 in cap 164 and mandrel 163.

For this purpose, mandrel 168 has an upper llange section i12 extending through opening 1&6 inrcap M4. lvlandrel 163 is co-terminous with the upper face of cap 164 and is spaced from the periphery or recess tl to form the annular, vertical discharge chamber or passageway and orifice llt? therebetween for the upward extrusion of the tubular body C.

In accordance with the invention, means areV provided for subjecting the flowing mass of swollen collagen fibrils to the shearing action of a rotating planar disc prior to the extrusion through the orifice lill. Preferably, in accordance with the invention, this rotating disc is located so that the fluid mass will be caused to travel in contact with its rotating lower surface, thence around the perimeter of the rotating disc and across its upper surface through passageways defined between the rotating lower and upper faces of said disc, and planar surfaces lying above and below said disc. As shown, the disc lla, which is relatively thin and of wide diameter, is mounted to rotate about the central axis of the extruder, being formed as a head or flange on the tubular drive shaft 116 which extends downwardly from the lower face of the disc through the central aperture in block 192 beyond the lower end thereof. The downwardly projecting end of shaft 115 is provided with an externally mounted ring gear 129 which is adapted to be driven by any suitable gearing and drive source, not shown. The gear 12d is formed as part of a sleeve l22 which embraces the lower end of shaft 116 and is fixed thereto as by the setscrew 123.

As appears from the drawings, *te disc 14 is of a relatively wide diameter and shallow depth. lts upper surface 136 and its lower surface 132 are both liat planar surfaces extending substantially the total diameter of the disc beyond the central drive shaft or shell 116.

In accordance with the invention, eans are provided for causing the fluid mass of swollen collagen fibrils to travel smoothly under pressure in a mixing chamber from near the inner or central portion of the lower face 132 of disc 1M in a radially outward path across the bottom face of the disc where the material in the mass is subjected to a rotary shearing action as described above. Also, this first or lowermost passageway is designed to decrease in depth outwardly toward the perimeter of the disc so that the shearing action between the bottom of the rotating disc and the opposing planar face of the member im. is increased in intensity as the material travels across the bottom of the disc. For this purpose, the upper interior surface of the housing 102 is formed with as a cylindrical chamber or cup 134i underlying the major part of the bottom surface 132 of disc llfl. The bottom planar surface 136 of chamber l34 is, as shown, inclined downwardly and centrally so as to provide a planar surface below the disc of essentially triangular cross-section, with the deeper zone thereof adjacent the central portion of the extruder.

As will be seen in the lefthand portion of FIG. 4, means are provided for feeding the fluid mass centrally of the mixing chamber 134 from the inlet conduit lili?. For this purpose, a bore 138 communicates with the inner threaded end of conduit 169 and leads inwardly and thence upwardly to feed the material adjacent the deeper end or portion of the chamber i3d. Vv'hile only one such inlet is shown, a plurality thereof may be provided to feed the material at different spaced points around and adiacent to the inner lower portion of chamber 134.

Preferably, the planar inclined surface i3d extends upwardly and outwardly to near the perimeter of disc iid but is flattened there to form the horizontal annular surface The terminal portion of the lowermost planar passageway is horizontal ln accordance v ith the invention, the fluid material is caused to travel vertically upwardly when it reaches the perimeter of the rotating disc and thence to travel radially inwardly across the top of the rotating disc until it reaches the lextrusion Vorifice 11G. For this purpose, a vertical passageway i44- is provided between the perimeter of the vertical edge of rotating disc 114 and cooperating edge SL46 formed in the block lll2. A relatively narrow iiat horizontal passageway -GS is provided between the top of the flat rotating disc 139 and the lower fiat horizontal face i559 of the upper block lmember ldd for he inwardly radial, Visco-elastic travel of the fluid material. rfhis passageway 148 communicates at the inner or central part thereof with the vertical extrusion chamber Y and orifice lill.

ln accordance with the invention, and as described more fully in connection with FlG. l hereinafter, means are provided for subjecting the extruding tubular body C to a coagulating treatment as soon as it emerges from the extrusion orifice. For this purpose, both the interior wall and the exterior wall of the rising tubular body are immersed in rising columns of coagulating liquid as soon as the tubular body emerges from the extrusion orifice. For providing the interior column of said liquid, the central opening of the hollow mandrel i553 is employed.

The casing tubing produced by the extfuder of FIG. 4 as well as those hereinafter described) is generally uniform and homogeneous. From microscopic examination it appears that the collagen fibrils constituting the casing wall are randomly oriented but lying parallel to the curved planes forming the surface of the tubular casing wall. FIGS. 5 and 6 are enlarged schematic views of this arrangement of collagen fibrils as they appear to exist in the freshly extruded casing wall before drying.

This arrangement is apparently accomplished by the rotating disc faces cooperating with the opposed planar faces defining the upper and lower mixing passageways. As discussed above, substantially all of the collagen mass in said passageways, especially in the upper one, is influenced by one or the other of the planar faces of the disc and/or the opposed faces of the housing. Normally, collagen fibrils tend to be oriented in the direction of extrusion. With the faces 30 and ll, for example, imparting opposite transverse shearing actions to the top and bottom portions of the collagen mass which is moving radially inwardly thorugh upper passage 25.48, the collagen fibrils therein are subjected to a combination of forces. However, these rotational shearing forces are generally in planes parallel to the linear extrusion force. Therefore, the collagen fibrils appear to become disposed parallel to the planar faces of the passageway. This apparent random but parallel disposition is believed to be retained as the brils move through the relatively short discharge vertical chamber lli? and are extruded in the form of a tubular collagen casing having the collagen fibrils thereof randomly oriented but lying parallel to the surface of the tubular casing wall. Those fibrils in the zones nearest the vertical cylindrical walls of the chamber lli? may orient themselves somewhat longitudinally, thereby adding to the longitudinal tensile strength of the final casing.

Referring now to the embodiment represented by FIG. 1, the extruder assembly lil is there shown in considerably greater detail. ln comparison with the rather simple and diagrammatic showing of HG. 4 with a rotating disc between stationary planar surfaces, the extruder of FIG. l provides planar surfas on either side of a rotating disc which surfaces themselves rotate in direction opposite to that of the disc, thereby increasing the rotary planar forces imparted to the fluid fibrillar mass being extruded. Assembly itl is preferably mounted for vertical delivery to extrude the watery mass of collagen fibrils in the form of a tubular body into a recirculating dehydrating or coagulating bath which flows axially in contact with both the irmer and outer walls of the tubular body. By the coagulating and subsequent treatments the tubular body is ultimately reduced in wall thickness from a tube having a wall thickness of, eg., i4 mils, to a very thin dry tube having a wall thickness of the order of l mil, as described in greater detail in copending application, Serial No. 82,934, tiled as of even date herewith.

Extruder assembly lll comprises a generally cylindrical, stationary housing l2 to which is fixed a top capl section 14 and a bottom section la by means of bolts i7. Sections 14 and 16 enclose the ends of housing l2, and suitable framework (not shown) fined to housing l2 supports extruder lil in vertical position.

The main central support for the moving parts of the extruder is provided by a hollow mandrel l co-axially fixed in the housing l2 in spaced relationship thereto. The mandrel has an upper stepped section i9 which extends through an accommodating central recess l5 in the cap ld and is co-terminous with'the upper surface 2li of 1 1 the cap. The outer cylindrical surface of section 19 is spaced from the periphery of recess while the step 13 proper is curved and spaced from the complementary underface of cap i4 to form a stationary discharge passage 17 comprised of a longitudinal annular section 21 interconnecting with a lateral planar section 23.

The lower end of mandrel 18 passes through a suitable central opening in bottom 16 and is provided with a terminal ange section 22 which bears against the overlying face of bottom 16 and is secured thereagainst by bolts 12, only one of which is shown. To facilitate assembly of extruder 1t? in operative position as shown, mandrel 1S is recessed at its lower end to accommodate a threaded hollow insert 24.

in accordance with the invention, the mass of swollen collagen fibrils to be extruded is caused to pass between the relatively rotating planar faces of two rotatable disc members. As embodied, a pair of nested, spaced, concentricaliy disposed, inner and outer disc members 2S and 30 are mounted for rotation relative to each other, preferably counter-directionally, about the central axis of the extruder. The innermost disc member 28 includes a flat, disc-like upper section 32 fixed to and extending laterally from a tubular drive shaft 34 which surrounds mandrel 18. The outermost disc member 30 is bifurcated to embrace inner disc 23, being formed with an upper horizontal disc member 36 secured to a lower horizontal disc member 4i) formed on the upper end of an outer, concentric, vertical tubular drive shaft 42.

Disc member 3i) has a generally planar underface 44 on the base portion 46 which extends inwardly from section 36. Underface 44- extends parallel to and in adjacent spaced relation with the upper face 48 of disc section 32 to define an uppermost, generally planar relatively narrow extrusion passage Sil therebetween which is smooth and uninterrupted. A lowermost, generally planar mixing chamber 51 is also formed between the upper face 52 of disc 4@ and the underface of interior disc 32. Chamber 51, which is somewhat deeper than extrusion passage Si), interconnects therewith around the circumferential edge 5d of disc 32 to form a smooth continuous path for the uid mass across passage 5@ to discharge chamber 17. For distributing fibrillar collagen fluid to said chamber and passageways, the upper inner surface of shaft 42 is formed with an annular shoulder 41 which extends inwardly adjacent the outer peripheral wall of shaft 34, defining the lower end of an annular distributing chamber 43 between shafts 42 and 34. The upper end of passage 43 communicates with chamber 51, as shown. An annular sealing ring 45' seals the lower end of chamber 43 to prevent contamination of the collagen mass therein.

Drive shafts 34 and 42 are concentrically disposed in co-axial spaced relationsfrp in housing 12, as shown in FIG. l, with inner drive shaft 34 positioned adjacent mandrel 1S and outer drive shaft 42 radially displaced outwardly therefrom.

To rotate drive shafts 34 and 42, they are each pro- Vvided at their lower ends with bevel gear assemblies t) and 62, respectively. Gear assembly 62 includes a lock nut 61 'threaded on the outer face of shaft 42 with bevel gear 63 fixed to lock nut eil by bolts 65. Gear assembly di? comprises a gear hub 67 threaded on the outer face of shaft 34, with bevel gear 69 secured to gear hub e7 by Vbolts 71. The bevels of gears 63 and 69 are oppositely disposed for engagement by a common pinion 64. Rotation of pinion d4 rotates shafts 34 and 42 and, consequently, disc members and Si? in opposite directions.

Pinion 64 is fixed on one end of a shaft 66 journalled in spaced bearings 63 and iii mounted in a bearing housing 72 recessed into the wall of housing 12. Cap 74 circling shaft ed closes bearing housing 72 and is readily removable to provide access to the bearin g when necessary.

. ShaftV de is driven by a suitable power source such as a motor and gearing (not shown) to effect opposite rotation of members 2S and 30.

Drive shafts 42 and 34 are Vheld in spaced radial and axial alignment in housing 12 as follows:

The outer periphery of shaft 42 adjacent lip 46 has a shoulder 76 formed thereon which rests on the inner race of a bearing Si) located between the outer periphery of shaft 42 and the inner periphery of housing 12. The inner race of bearing S0, in turn, is supported on a washer S2, seated on the inner race of a second bearing 84, the outer race of which rests on an anular shelf 86 formed on the mner periphery of housing 12. The inner race of bearing 84 rests on the upper face of lock nut 61 which maintains the assembly in xed axial position. Set screw 7 8 threaded for travel in the wall of housing 12 is operative to support the outer race of bearing 8i? and to maintain bearings Si) and 84 in spaced alignment between housing 12 and shaft 42.

The upper end of shaft 34 is radially offset outwardly adjacent shoulder 4i, forming an annular ridge 8S on the outer periphery thereof. Ridge 8S rests on the inner race of a bearing 90, in turn supported on a sleeve 92 seated on a second bearing g4 between shafts 42 and The outer race of bearing 904 supports the underface of shoulder 41. A lock nut `96 threaded on the outer periphery of shaft 34 supports bearing `94 and maintains the entire assembly in axial position between shafts 42; and 34. Set screw 93 threaded for travel in the wall of shaft 42 is operative to support the outer race of bearing 9b and maintain it in aligned relationship against shafts v452. and 34 while a thrust washer 160i assists in maintaining shaft 42 and gear hub 67 on shaft 34 in spaced axial alignment. Preferably, the space between members 2S and 3d below passage 43 and the space between the outer periphery of member 30 and the inner periphery of housing '12 are charged with a suitable lubricant such as glycerol. Sealing ring y161 isolates discharge chamber 17 from the interior of housing 12 to prevent seepage of the lubricant into chamber 17.

The homogenized duid mass of swollen collagen fibrils pre-pared as described above, is fed under pressure by suitable pumps (not shown) to extruder 10 through a feed line 162. The collagen mass from feed line 162 is pumped through an interconnecting bore 164 formed in bottom 1'6 and aligned opening 166 in mandrel 18 into an elongated axially extending annular passage 16S.

To form passage 16S, a sleeve 17d is disposed concentrically within mandrel .18. The inner wall of mandrel 18 in the vicinity of sleeve 170' is recessed a-s at 172. The lower end of annular passage 163 is sealed by sealing ring 174 to isolate passage 158 from the interior of sleeve 170.

The collagen mass entering passage 168 travels upwardly therein. Near the upper end of its passage, the collagen mass passes through a plurality of radially spaced outlet ports 1'7-6 in mandrel 18 into an annular receiving chamber 17S. Chamber 178 is formed by the radial olset 8S of shaft 34 and-is defined by the outer cylindrical surface of stationary mandrel 18, the inner cylindrical surface of movable shaft 34, the underface of disc 32 and the upper face of ridge Sb. Opposed annular sealing rings 179 isolate the upper and lower extremities of chamber 178 to prevent contamination of the collagen mass by the extruder lubricant. From chamber 178, the collagenous mass is fed through a second group of spaced radial ports 18@ formed in shaft 34 which provide Iestricted communication with annular distributing chamber 43.

An initial mixing of the collagen fibrils is accomplished as the collagen is fed through ports 180 lsince these ports 180l formed in shaft 34 are normally rotating during the collagen feed.

The fluid collagen mass in chamber 43 is subjected to a second preliminary mixing or blending since the members defining chamber 43 are being rotated in opposite directions. From chamber 43, the collagen mass is travelled into the laterally-extending planar mixing chamber alaaf/ss 51. ln chamber l, a thorough homogenization is effected by the action of the oppositely-rotating generally planar surfaces S2 and 55.-. Surfaces 52 and S4 break up or disperse any collagen bril agglomerates in the iluid mass. These agglomerates or accumulations of collagen fibrils sometimes occur in the swollen collagen mass despite the iltering steps in the preparation of the extrusion materid. Swollen collagen fibrils possess generally rubber-like elasticity. The swollen collagen libril agglomerates are able to adapt themselves to the filter openings, becoming attenuated to lit through the ilter and resuming their agglomerate condition once they have passed through the tilter constrictions.

To disperse these agglomerates into their individual swollen ibril components, the invention applies a direct dispersing force thereto. Surfaces 52 and 54 impart a shearing action to the collagen mass moving through chamber 51. This shearing action applies the dispersing force to the collagen mass and tends to break up or disperse the collagen llbril agglomerates in the mass. The shearing action of surfaces 52 and 5d is generally transverse to the direction of movement of the collagen mass which is travelled radially outwardly in chamber 59.

At the periphery of disc 32, the fluid mass in chamber 5d passes around edge 5S into extrusion passage Sil. In passage 56, the homogenization of the iluid ibrillar Collagen mass is completed by the oppositely rotating planar faces 44 and 4% defining passage 5l?. Faces de and 43 impart a second transverse shearing action to the collagen mass moving radially inwardly of disc 32 toward discharge chamber :17. This second transverse shearing action ensures that any remaining collagen ibril agglomerates are dispersed before discharge of the collagen mass in tubular form.

As previously noted, upper passage Sil' is narrower or shallower than lower chamber 5l. Thus in passage 5i?, substantially the entire collagen mass is aected by one or the other or" faces 44 and 4d forming pasage Sil. By imparting a transverse shearing action to the entire epth of the collagen mass in passage Si), substantially all remaining collagen agglomerates are subjected to this shearing action and are eliminated from the mass prior to discharge.

The swollen collagen mass in passage 50 is travelled radially inwardly between rotating faces and l into aligned planar section 23 of stationary discharge chamber 17 whence it is extruded upwardly through longitudinal annular section 2l thereof in the fori.- a continuous tube into a recirculating dehydrating bath.

The dehydrating or coagulating bath is recirculated in an enclosed system which incluces a cylindrical distributor element 1&2 which surrounds recess l5 in cap ld adjacent the discharge chamber 17. A vertical column "alle is supported on distributor l' with the interior of the column ld in communicati n with distributor 122. The coagulating liquid enters dis ributor l?. through conduit 13e and an aligned bore 1&3 in the wall of distributor 182 and hence into column Where it iiows vertically upward against the o ide of the extruded tubing.

The coagulating liquid is also supplied to the inside of the extruded tubing through another conduit 19d which communicates with the interior of mandrel 13. The portion o the liquid entering from the conduit if-T flows .iL/4; upwardly inside the mandrel into contact Iwith the inner wall of the extruded tubing but at a considerably slower rate of ilow than that of the liquid ilowing along the exterior of the tubing, thereby to protect the walls thereof from disruption and undue liquid friction. The portion of the liquid inside the tubing is returned through overflow tube .192 axially disposed within mandrel l and extending upwardly to the tip of column The portion of the liquid entering column 1355 through distributor 152 and in Contact with the outer periphery of the extruded casing is discharged at the top or" the column ld into a reservoir (not shown).

inasmuch as the density of the extruded tubular body is substantially less than that of the coagulating liquid (eg, a solution of 40% ammonium sulfate) the tubular body tends to lloat upwardly in the coagulating baths, thereby reducing the amount of pull required to move it to subsequent conditioning treatments.

Another advantage achieved by use of extruder 16 (as well as by the other forms of extruder shown herein) is the beneficial utilization of the Visco-elastic characteristics of the lluid librillar mass of swollen collagen to reduce the extrusion pressures required. The amount of circular tension developed in such a mass is directly proportional to the length of time the material is subjected to the rotational forces applied and to the amount of material rotated.

In chamber 51, the tendency of the Visco-elastic collagen mass to travel centripetally under circular tension must be overcome because said mass is being travelled radially outwardly under hydraulic feed pressure while rotated by members 28 and 38. However, the viscoelastic phenomenon is extremely advantageous when the mass reaches passage 50, which, as shown, is longer and shallower than chamber 51, so that substantially the entire collagen mass therein is affected by rotation of either one or the other of faces 44, 48. Therefore, in moving through passage 50, the collagen mass undergoes a more complete application of the rotary forces and therefore a greater amount of circular tension is developed therein. rl`hus, the counter-dow effect of circular tension developed in the collagen mass as it travels radially outwardly through chamber 51 is more than compensated by the desired centripetal ow thereof under the greater circular tension developed in passage Si?.

To illustrate this in practice, with elements 23 and 3i) rotating at 10G-125 r.p.m. in opposite directions during the swollen collagen feed, a hydraulic feed pressure of l0-50 p.s.i. is required to extrude continuously twenty- Itive feet of tubing per minute, while with elements 28 and 3@ stopped, a pressure of 70-90 p.s.i. is needed to continuously extrude twentydive feet of casing per minute. The lower extrusion pressures are the result of utilizing the Visco-elastic properties of the plastic collagen mass to assist in extruding the mass in continuous tubular form.

lt will be understood that like numerals designate parts of like construction and operation in FIGS. 1, 2 and 3.

FlG. 2 discloses a modied form of extruder wherein means are provided for extruding the duid collagen mass in tubular form through a short annular discharge or orice chamber formed of oppositely rotating chamber walls, rather than through a stationary orifice chamber as in FIG. l. ln this embodiment, extruder 2li@ includes an outer housing 211 formed of a cylindrical section 212, an annular ange section 2id of generally L-shaped cross-section and an annular bottom flange section 2id. An annular cap 21S is fixed on annular ilange section 214 enclosing the upper section of housing 2li.

Extruder Zll includes a collagen brii distributing device, designated generally 217, co-axially disposed in housing 211. Device 2l? includes a pair of spaced concentrically disposed relatively rotatable members 21S and 22u mounted for rotation about the central axis of the extruder. The innermost member 213 includes a at disclike upper section 222 fixed to and extending laterally of an annular lange 219 formed on the upper end of a tubular drive shaft 224. The outermost member 22o is formed of an inverted cylindrical section 225 secured to an annular transverse 'flange or lip 22S formed on the upper end of a econd tubular drive shaft 230.

The planar inner face 232 of the base portion 234 of section 226 is mounted in adjacent spaced relation with respect to the upper face 236 of disc section 22,2 to define a generally planar radial extrusion passage 23S therebetween. ln addition, the upper face 2d@ or" lip 22S is partially inclined and forms with the underface 2452 of disc Z22 inverted, semi-irusto-conical, annular mixing 3, l chamber 244. Chamber 244 interconnects with extrusion passage 233 around the circumferential edge 246 of disc 222 to form a smooth and continuous fiuid path from the outer periphery of tubular drive shaft 224-.

Element 218is provided at its uppermost end with a relatively short, annular lip 247, at the center of disc 222 which extends through an accommodating central recess .248 in the base portion 234 of element 229. Lip 247 is co-terminous with the upper face 235 of base 234. Lip 247 may be formed integrally with shaft 224 or may be separately formed and suitably fixed on disc 222 or shaft 224. The periphery of central recess 248 is spaced from the outer cylindrical surface of lip 247 to form an annular discharge chamber d interconnected at its lower end to planar extrusion passage 23S and forming a transverse annular continuation thereof.

rive shafts 224 and 2343 are concentrically disposed in axial spaced relation in housing 211, as shown in FIG. 2. The shafts pass through bottom section V216 and are provided adjacent their lower ends with beveled gear assemblies 252 and 254, respectively. Gear assembly 252 includes an annular gear hub 256 threaded on the outer cylindrical surface of shaft 224 with a bevel gear 258 fixed to gear hub 256 by bolts 257. Gear assembly 254, in turn, comprises a gear hub 269' keyed in position on the outer cylindrical face of shaft 23# at a distance above the lowermost end of the shaft. A bevel gear 262 is secured to gear hub 269 by bolts 261. The bevels of gears 25S and 262 are oppositely disposed from engagement by a common inion 264. The rotation of pinion 264 rotates shafts 234 and 239, and, consequently, members 218 and 220 in opposite directions. Pinion 264 is similar in construction and operation to pinion 64 of the previously described embodiment.

The lower end of shaft 234 passes through an accommodating passage in bottom portion 231 of shaft 239, and shafts 224 and 230 are held in spaced radial and axial alignment in housing 211 as follows:

A pair of spaced bearings 266 and 263 are disposed between the outer cylindrical periphery of shaft 23? and the inner cylindrical periphery of section 212. Lowermost bearing 268 rests on bottom section 216 and the bearings are locked in position by the Vouter periphery of shaft 23d by snap ring 270 on the outer periphery of shaft 23th Spacer ring 272 and sealing ring 274 isolate the interior of the bearings 266 and 26S to permit lubrication of the bearing assembly without the possibility of contaminating the rest of the extruder.

The underface of ange 219 rests on a bearing 276 disposed between shaft 224 and 230. Bearing 276, in turn, rests on a sleeve 278 supported on a second bearing 287i) seated on bottom 23!` of shaft 230 and disposed between shafts 224 and 230. Snap ring 281 on the outer periphery of shaft 224 assists in supporting bearing 284). Spaced annular sealing rings 282 and 234 isolate the interior of the bearings 276 and 28@ to permit lubrication of the bearing assembly.

The lowermost end of inner shaft 224 is uncapped and disposed in the upper end of open housing 236. Shaft 224 fits snugly into housing 286, enclosing the upper end thereof.

In operation, a homogenized mass of swollen collagen brils is prepared as described for the previous embodiments. Said mass is fed under pressure by a feed line (not shown) through a bore 28S in the Ycylindrical wall of housing 2S6 andinto a sealed, annular recess 2% formed in the inner cylindrical wall of the housing. From lrecess 291i, the mass is fed through spaced radial ports trically within shaft 224. The inner wall of the shaft is recessed in the vicinity of the sleeve 295, as at 293, and the sleeve fixed thereto. A sealing ring 291 seals the tea,

yes

l lower end of passage 294, isolating the passage from the interior ofthe sleeve 295.

The iiuid mass in passage 294 is travelled longitudinally upwardly through rotating shaft 224. Near the upper end of its passage, the mass passes through a plurality of spaced radial bores 296 in the upper end of shaft 224 which provide restricted communication with the annular mixing chamber 244.

As in the previous embodiment, the fluid mass of swollen collagen fibrils is travelled radially outwardly in chamber 244 between the counter-rotating elements 218 and 2249. At the periphery of disc 222, the mass passes around edge 246 thereof into the narrow, planar, extrusion passage 23S. The mass is again subjected to the action of the counter-rotating elements 213 and 220 as it moves radially inward through passage 23S toward the transverse, annular discharge chamber 256 formed by lip 247 and base 234 of element 22), which are rotating in opposite directions. The mass in chamber 250 is extruded therefrom in continuous tubular form through an accommodating opening 2&8 into a recirculating dehydrating bath.

FlG. 3 discloses another modified form of the invention. In this embodiment, the casing is extruded through an annular discharge chamber formed by oppositely rotating wall members which is substantially longer than that shown in FIG. 2.

ln most respects, the extruder 31@ of the present modiication is similar in construction and operation to extruder 219 disclosed in FIG. 2. However, in this modification base 234 is provided with an annular, longitudinally extending wall 312 at the periphery of central recess 243. Disc 222 of FlG. 2 is replaced by disc 314 which is similar in construction and operation to disc 222 but is of substantially greater thickness to more easily withstandV Disc 314 includes an elongated,V

the extrusion pressures. central, annular lip Slo which cooperates with wall 312 to form an elongated annular discharge chamber 31S therebetween. Wall 312 and lip 316 are co-terminous with the upper end of housing 211. Chamber 31S is disposed generally transverse to extrusion passage 320 formed by base 234 and disc 319, but communicates therewith at its lower end. Passage 32@ is similar to passage 238 of FlG. 2.

The mass of swollen collagen fibrils, prepared as in the previous embodiments, is fed under pressure through interconnected passage 294, chamber 244 and extrusion passage 32tl. Shafts 224 and 230 are rotated in opposite directions to eiect the uniform distribution of the collagen fibrils as in the previous embodiments. 'The collagen mass in extrusion passage 320 is extruded through elongated, annular discharge chamber 328 as a tubular body into the recirculating dehydrating bath thereabove. ln this embodiment, the collagen fibrils are extruded through an elongated annular discharge chamber 318 formed by the oppositely rotating members 312 and 316. The casing tubing produced in accordance with any em- Y bodiment of the present invention may be coagulated, hardened, dried, shirred and linked to form a readily cookable and edible sausage product.

While the invention has been described in detail according to the preferredV manner of carrying out the method and the devices embodying the invention, it will be obvious to those skilled in the art, after understanding the invention, that changes and modifications may be made therein without departing from the spirit or scope of the invention, and it is intended in the appended claims to cover such changes and modifications.

What Vis claimed is: Y

l. The method of extruding a tubular body containing collagen which comprises feeding under pressure a cool fluid mass of swollen collagen fibrils having a collagen solids content between 2.5% and 6% by weight into a f passageway between opposed planar surfaces said passageways being substantially greater in length than depth,

17 rotating said surfaces relative to each other to impart shearing forces to said mass and then extruding said mass as a tubular body with the inner and outer walls of said tube being formed from the respective portions of said mass moving contiguous to and manipulated by said surfaces.

2. The method of extruding a tubular body containing collagen which comprises feeding under pressure a cool fluid mass of swollen collagen fibrils having a collagen solids content between 2.5% and 6% by weight into a passageway between opposed planar surfaces, rotating said surfaces in opposite directions to impart equal but opposite shearing forces to said mass and then extruding said mass as a tubular body with the inner and outer walls of said tube being formed from the respective portions of said mass moving contiguous to and manipulated by said surfaces.

3. The method of extruding a tubular body containing collagen which comprises feeding under pressure a cool fluid mass of swollen collagen fibrils content between 2.5 and 6% by weight into and through a pair of interconnected continuous superposed passages between opposed planar surfaces, rotating said surfaces relative to each other to impart shearing forces to said mass as it is travelled through said passages, and extruding said mass as a tubular body with the inner and outer walls of said tube being formed from the respective portions of said mass moving contiguous to and manipulated by said surfaces.

4. An extruder for forming a tubular body in a fluid mass of swollen collagen Vfibrils having a collagen solids content above about 2,5% and below about 6% including in combination:

a disc rotatable about the central axis of the extruder;

a planar surface below and spaced from the lower surface of the disc to -form a smooth and Continuous radial first passageway for flow `of said iluid between said surfaces;

a second planar surface `above and spaced from the upper surface of said disc to form a second passageway for flow of said fluid therebetween;

means for rmoving said fluid mass through said lfirst passageway and in a reverse direction through said second passageway;

means for rotating said disc to eect relative rotational movement of said surfaces to impart a shearing force to said fluid mass therebetween;

and a tubular discharge orifice. communicating with said second passageway.

5. An extruder for forming a tubular body from a fluid mass of swollen collagen fibrils having a collagen solids content above 2.5% comprising in combination:

a disc;

means mounting said disc for rotation about the central axis of the extruder;

a planar surface below and spaced from the lower surfa of the disc to form a smooth .and continuous radial first passageway for flow of said fluid therebetween;

a second planar surface above and spaced from the upper surface of said disc to yform a second passageway for flow of said fluid therebetween;

said first and second passageways corrununicating around the perimeter of said disc to form a continuous path of travel for said fluid mass between said surfaces;

said passageways being of substantially greater length th-an depth;

means for moving said fluid mass through said lower and upper passageways;

.means for rotating said disc to effect relative rotational movement of said surfaces to impart a shearing force to said fluid mass therebetween;

`and a tubular discharge orifice communicating with said upper passageway.

6. An extruder fo-r forming a tubular bodyiof swollen collagen yfibrils having a collagen solids content of between 2.5 and 6% including in combination:

a disc having genenally flat upper and lower surfaces;

a tubular shaft supporting said ydisc for rotation about the central axis of the extnuder;

a smooth planar surface below and spaced from the lower sunface of said disc to form a smooth first radial passage for flow of said fluid;

a second smooth planar surface above and spaced with the upper surface of said disc to form a second smooth planar passage for flow of said fluid therebetween;

said first and second passages communicating around the perimeter of said disc to form a smooth, continuous path of travel for said fluid mass between said surfaces;

means interconneming said planar surfaces forming a housing for said disc to enclose said path of travel of said fluid mass;

an elongated, annular ldelivery chamber axially disposed in said tubular shaft;

means communicating said delivery chamber and said `first planar passage;

means for flowing said fluid mass axially through said delivery chamber and outwardly of said disc through said `first passage and inwardly of said `disc through said second passage;

means for rotating said tubular shaft `to effect relative rotational movement of said surfaces to impart a lshearing force to said fluid mass therebetween;

and a central tubular discharge orice communicating with said second passage.

7. An extruder for forming a tubular body of swollen collagen fibrils having a collagen solids content of between 2.5% and 6% including in combination:

a disc having generally at upper and lower surfaces;

a tubular shaft supporting said disc for rotation about the central axis of the extruder;

a planar surface below and spaced from the lower surface of said disc to form a first passage for radial flow of said fluid;

a second planar surface above and in adjacent spaced relationship with the upper surface of said disc to form a second planar passage for flow of said fluid therebetween;

said second passage being of smaller depth than said first passage and said passages being of substantially greater length than depth;

said first and second passages communicating around the perimeter of said disc to form a smooth, continuous path of travel for said fluid mass;

means interconnecting said planar surfaces and forming a housing for said disc to enclose said path of travel of said fluid mass;

an elongated, annular delivery chamber axially disposed in said tubular shaft;

means mounting said planar surfaces for rotation concentric with said disc but in the opposite direction;

means communicating said delivery chamber and said first planar passage;

means for flowing said fluid mass axially through said delivery chamber and outwardly of said disc through said first passage and inwardly of said disc through said second passage;

means for rotating said planar surfaces and said tubular shaft in opposite directions to impart a shearing force to said fluid mass therebetween;

and a central tubular discharge orifice communicating with said second passage.

8. An extruder for forming a tubular body of collagen having a collagen solids content of between 2.5 and 6% including in combination:

a disc having generally flat upper and lower surfaces;

a tubular shaft supporting said disc for rotation about the central axis of the extruder;

a planar surface below and spaced from the lower surface of said disc to form a lirst passage for flow of said fluid;

a'second planar surface above and spaced from the upper surface of said disc to form a second planar passage for iiow of said uid therebetween;

said rst and second passages communicating around the perimeter of said disc to form a continuous path of travel for said iiuid mass between said surfaces;

a hollow cylindrical mandrel;

means securing said mandrel in position axially inside said tubular shaft;

an elongated annular delivery chamber formed in said mandrel;

a plurality of cooperating radial bores through the cylindrical walls of said mandrel and said cylindrical shaft, said bores communicating said delivery chamber with said iirst planar passage;

an outer housing for said extruder;

` means for mounting said planar surfaces for concentric rotation with said disc, but in the opposite direction thereto; Y

means for flowing said uid mass axially through said delivery chamber and outwardly of said disc through Y said first passage and inwardly of said disc through said second passage;

means for rotating said tubular shaft and said planar surfaces to impart a shearing force to said fluid mass therebetween;

a central tubular discharge orifice communicating with said second planar surface and forming a transverse continuation thereof, said orilice including a central circular opening in said outer housing;

and an extension on said mandrel extending axially through said disc and said upper planar surface and concentrically disposed in said housing in spaced relation with the periphery of said opening to define a stationary discharge orifice. Y

9. An extruderl for forming a tubular body from a mass of collagen Vfibrils which comprises:

a housing; v

a disc rotatable about an axis within said housing;

means including one surface of said disc constituting a lirst radial passageway through which the material to be extruded may iiow outwardly; A

means including the other surface of said disc constituting a second radial passageway through which said material may flow inwardly;

apassageway interconnecting said radial passageways;

and

a tubular discharge orifice communicating with said second passageway;

said disc, upon rotation, being adapted to impart shearing forces to the material traversing said passageways. v

10. The method of extruding a tubular body from a fluid mass of swollen collagen ibrils having a collagen solids Vcontent of at least 2.5% and below 6% by weight which comprises feeding said fluid mass under pressure to a tubular extrusion orifice and eliminating boundary effects in said collagen mass by imparting transverse, rotary while owing said collagen mass in closed arcuate paths to said extrusion orifice shearing forces to said mass during the extrusion process.

1l. The method of extruding a tubular body from a fluid mass of swollen collagen fibrils having a collagen solids content between 2.5 and 6%V by weight which comprises feeding said duid mass to a tubular extrusion orifice, eliminating boundary effects in said collagen mass by imparting transverse rotary equal but opposed shearing forces to said mass during the extrusion process and preventing development of boundary effects in said mass during extrusion by flowing said collagen mass in continuous curved paths to said extrusion orifice.

12. The method of extruding a tubular body from a iiuid mass of swollen collagen fibrils which comprises feeding said uid mass under pressure toward a tubular extrusion orice and obliterating the formation of boundary surfaces in said mass by moving said mass continuously in closed circular paths while subjecting it to transverse rotary shearing forces.

References Cited in the tile of this patent UNlTED STATES PATENTS Becker June 13, 1939 2,337,775 Schultz Dec. 28, 1943 l2,896,254v Braun July 28, 1959 2,977,632 Bunch Apr. 4, 1961 FOREIGN PATENTS 672,035 Germany Feb. 18, 1939 104,023 Sweden Mar. 17, 19'42 522,586 Canada Mar. 13, 1956 OTHERv REFERENCES Maxwell and Scalora: The Elastic Melt Extruder-Work Without Screw, in Plastics Engineering pages 107-210, October 1959, i

UNITED STATESPTENT orties CERTIFICATE 0F QRRECHN Patent No 3122,788 March 3, 1964 Emanuel Roy Lieberman 1t is hereby certified that error appears iny the above numbered patentgreq'iiring correction and that the said Letters Patent should read as corrected below..

Column 9 line 18, for "14" read 114 F-; co1umn 10, line 29, for "thorugh" read through column 20, lines 13 to 16, strike out "rotary while flowing said collagen mass in o1osed arcuate paths to said extrusion orifice shearing forces to said mass during the extrusion process," and insert instead rotary, shearing forces to said mass during the extrusion ggrocess, while flowing said collagen mass in closed arcuate paths to said extrusion orificeo Signed and sealed this 29th day of December 1964a (SEAL) Attest:

:ERNEST W. SWIDER EDWARD J. BRENNER -Atestng Ufficer Commissioner of Patents 

1. THE METHOD OF EXTRUDING A TUBULAR BODY CONTAINING COLLAGEN WHICH COMPRISES FEEDING UNDER PRESSURE A COOL FLUID MASS OF SWOLLEN COLLAGEN FIBRILS HAVING A COLLAGEN SOLIDS CONTENT BETWEEN 2.5% AND 6% BY WEIGHT INTO A PASSAGEWAY BETWEEN OPPOSED PLANAR SURFACES SAID PASSAGEWAYS BEING SUBSTANTIALLY GREATER IN LENGTH THAN DEPTH, ROTATING SAID SURFACES RELATIVE TO EACH OTHER TO IMPART SHEARING FORCES TO SAID MASS AND THEN EXTRUDING SAID MASS AS A TUBULAR BODY WITH THE INNER AND OUTER WALLS OF SAID TUBE BEING FORMED FROM THE RESPECTIVE PORTIONS OF SAID MASS MOVING CONTIGUOUS TO AND MANIPULATED BY SAID SURFACES. 